1. Field of the Invention
The present invention relates to an extension structure for a tool, and more particularly to a socket wrench extension structure.
2. Description of the Related Art
A first conventional socket wrench extension 10 in accordance with the prior art shown in FIG. 1 includes a first end formed with a connector 12 which can be coupled with a socket (not shown), and a second end formed with an enlarged head 14 which defines a square recess (not shown) therein for receiving a square head (not shown) of a socket wrench (not shown). The connector 12 includes a ball (not shown) provided thereon so that the socket can be tightly mounted on the connector 12 of the socket wrench extension 10. However, the user has to exert a large force for detaching the socket from the connector 12 of the socket wrench extension 10 so that the socket cannot be quickly mounted on or detached from the connector 12 of the socket extension shank 10, thereby causing inconvenience in operation of the socket extension shank 10.
A second conventional socket wrench extension 20 in accordance with the prior art shown in FIG. 2 includes a first end formed with a connector 22 for coupling with a socket (not shown), and a second end formed with an enlarged head 24 defining a hexagonal recess 21 therein for driving a screw (not shown). However, the user also has to exert a large force for detaching the socket from the connector 22 of the socket wrench extension 20 so that the socket cannot be quickly mounted on or detached from the connector 22 of the socket extension shank 20, thereby causing inconvenience in operation of the socket extension shank 20.
The closest prior arts of which the applicant is aware are disclosed in the following patents:
1. U.S. Pat. No. 5,289,745; PA1 2. U.S. Pat. No. 5,720,207; PA1 3. U.S. Pat. No. 6,006,632; and PA1 4. U.S. Pat. No. 6,003,414.
In the above-mentioned four patens, an elongated channel is formed in the socket wrench extension so that the ball can be received into the connector of the socket wrench extension, thereby facilitating the socket being detached from the connector of the socket wrench extension. However, it is difficult to drill such an elongated channel in the socket wrench extension. In practice, a long drilling head with a smaller diameter is used for drilling the elongated channel in the socket wrench extension so that the drilling head is easily broken during the drilling process, thereby increasing the difficulty of working, increasing the time required for drilling the elongated channel, and increasing the cost of fabrication.
Another closest prior art of which the applicant is aware is disclosed in U.S. Pat. No. 5,813,296. In the above-mentioned patent, the ball can also be received into the connector of the socket wrench extension, thereby facilitating the socket being detached from the connector of the socket wrench extension. However, the socket wrench extension includes a complicated construction consisting of many parts, thereby greatly increasing the cost of fabrication.